Combustion apparatus with ignition means therefor



June 2, 1953 w, POUCHQT 2,640,321

COMBUSTION APPARATUS WITH IGNITION MEANS THEREFOR Filed March 22, 1950INVENTOR WITNESSE? Walter D. Pouchpt aw BY m. MN I ATTORNEY PatentedJune 2, 1953 COMBUSTION APPARATUS WITH IGNITION MEANS THEREFOR Walter B.Pouchot, Prospect Park, Pa., assignor to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a. corporation of PennsylvaniaApplication March 22, 1950, Serial No. 151,173

Claims.

This invention relates to combustion apparatus, more particularly toignition means therefor, and has for an object to provide improvedmechanism for igniting a fuel-air mixture.

When a mixture of fuel and air is flowing through a combustion tube orchamber at high velocities, for example in afterburners for jet engines,difficulty is frequently encountered in preventing the flame formationbeing swept downstream and out of the tube or chamber before combustionof the fuel-air mixture is completed.

One means previously proposed for overcoming this difficulty comprisedthe provision of a grid of thin plates or webs disposed generallytransversely of the combustion chamber together with a hollow airfoilsection member positioned upstream of the grid and provided with an upstream inlet for a portion of the fuel-air mixture and a downstreamoutlet for burning fuelair mixture, the hollow member being so disposedas to direct its flaming discharge onto a limited portion of each bar orweb of the grill to-heat the latter to a temperature sufficient toeffect surface ignition of the fuel-air mixture flowing in contacttherewith. In this prior arrangement it was necessary to rely on heattransfer through the material of the webs of the grid to extend theheating of the grill to a region thereof beyond that directly contactedby the discharge from the hollow heating member and hence to extend thesurface combustion effect to cover the entire cross-sectional area, orthe entire width, of the combustion chamber.

The present invention seeks to improve this prior arrangement bycombining the hollow heating member and the grid. To this end, the gridmembers are made hollow and a heater is directly united therewith insuch a manner that the burning gases pass from the heater into andthrough the hollow grid members to heat them internally to a temperaturesufficient to produce auto-ignition of the fuel-air mixture flowing incontact with the outer surf-aces of the grid members.

Accordingly, another object of the invention is to provide a surfaceignition member together with means for internally heating substantiallythe entire length thereof.

These and other objects are effected by the invention as will beapparent from the following description and claims taken in connectionwith the accompanying drawing, forming a part of this application, inwhich:

Fig. 1 is an elevational View of an aircraft power plant incorporatingthe invention, a portion of the structure being broken away in theinterest of clearness;

Fig. 2 is an enlarged fragmentary longitudinal sectional view showingdetails of the invention;

Fig. 3 is an elevational view of the right hand end of the structureshown in Fig. 2;

Fig. 4 is a sectional view similar to Fig. 2, but showing a modifiedconstruction; and

Figs. 5 and 6 are enlarged transverse sectional views showing theupstream ends of two additional arrangements of the invention.

Referring now to the drawing in greater detail, the invention, while inno way limited to use therewith, is shown in connection with theafterburner of a power plant for jet propulsion of aircraft. This powerplant, indicated in its entirety by the reference character It],comprises an outer casing II and a composite core structure I2 coaxialwith the longitudinal axis of the outer casing and spaced from thelatter radially to provide therebetween an annular passage I3 for flowof air and gas substantially straight through the power plant from aninlet M at the front, or left as viewed in Fig. 1, to an exhaust nozzleI5 at the rear or opposite end.

The composite core structure I2 includes a fairing cone Iii, axial-flowcompressor I'I, combustion apparatus I8, turbine I9 and tailcone 2|. Theoperation of a power plant of this type is well understood in the art,and may be summarized as follows: Air entering the annular passage I3through the inlet I4 is compressed in the compressor I! and then heatedin the combustion apparatus I8 by the burning of fuel therein. Theheated air and hot products of combustion are expanded through theblading of the turbine I9 to motivate the latter which in turn drivesthe compressor I1 through a connecting shaft (not shown). The motivefluid expanded through the turbine is discharged from the power plantthrough the exhaust nozzle I5 in the form of a jet establishing apropulsive thrust.

In the power plant herein illustrated, the exhaust nozzle I5 is disposeda material distance downstream from the turbine I9 and tai-lcone 2 I,the space therebetween being utilized as an afterburner combustion spaceor chamber 25 for further heating the air and gases discharged from theturbine prior to their exhaust through the exhaust nozzle I5.

Fuel is supplied to the afterburner 25 through a plurality of annularmanifolds 22 and supply lines 23 to effect a mixture of fuel and air forflow through, and combustion in, the afterburner.

Due to the relatively high velocity of the fuelair mixture flowingthrough the afterburner combustion chamber, difficulty may beencountered in obtaining suitable flame distribution transversely of thecombustion chamber unless special means are utilized to this end.

In accordance with the presentinvention, one or more surface ignitionmembers are disposed transversely of th combustion chamber and serve toignite the stream of fuel-air mixture passing iii-close proximitythereto. Inasmuchas the surface :ignitionmember or member extendsubstantially all of the way across the combustion chamber 25, they willeffect ignition of the fuelair mixture throughout substantially the fullwidth of the stream thereof.

In the form of the invention shown in Figs. 1, 2 and 3, a single surfaceignition device in the form of a tubular member 26 extends transverselyof the combustion chamber 25. Wall structure is associated with thetubular member 25 adjacent the center of the upstream edge thereof toprovide a heater 2? having an inlet 28 directed upstream for entry of alimited portion of the fuel-air mixture flowing through the afterburner.

The relatively high-velocity stream offuel-air mixture entering thevheater 2? expands after passing the narrow inlet 28, resulting in avelocity reduction of a degree sufficient to permit flame retention andpropagation in the heater 2'! and tube 28. Preferably, the tube 28 is ofairfoil sectionand is provided with one or more openings 29 in itsdownstream edge for discharge of burning gases and hot products ofcombustion, the flow of burning gases lengthwise through the tubeheating the walls thereof to or above the auto-ignition temperature ofthe fuel-air mixture flowing in contact with the outer ignitionsurfaces'of the tube. 7

Any suitable means may be provided for initiating combustion within theheater 21, an electric ignition coil 3i being shown for this purposeinFigs. 2 and 4.

The modification ofFig. 4 differs from that of Figs. 2 and 3 in thatadditional fuel-air inlet openings 32 are provided in the upstream edgeof the tube 26a, together with internal baffles 33 to prevent flow ofentering fuel-air directly across the width of the tube and out throughthe outlets 29a directly opposite.

Fl$$p and 6 show further desirable arrangements each involving the useof a plurality of tubes. In Fig. 5 a plurality of straight tubes 50 aredisposed in parallel side-by-side relation, providing a grid structuredisposed generally normal to the direction of flow of the fuel-airmixture through the combustion chamber. A single elongated heater 5|having an elongated slot-like fuel-air inlet 52 in its upstream edge,extends at rightangles to the plurality of tubes 50 and discharges tothe interior of each of the latter through outlets 53.

Each tube 50 is provided with one or more outlet openings in thedownstream side thereof.

In the construction of Fig. 6, a plurality of radial tubes 55 andcircular tubes 56 are arranged to provide a grid to which burning fueland air are supplied from a plurality of heaters 57 having inlets 58 anddischarging to the tube grid at intersections of radial and circulartubes, which tubes have one or more outlet openings in the downstreamsides thereof.

It will be apparent that the heaters 5| and 51 of Figs. 5 and 6,respectively, may be provided with any suitable means (not shown) forinitiating combustion within the heaters.

While the invention has been shown in several forms, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various change and modificationswithout departing fromthe spirit thereof.

What is claimed is:

1. In combustionapparatus. first wall struce ture defining. a maincombustion. chamber adapted for flow of air therethrough; means near theupstream end of said chamber, considered in the direction of flow of airtherethrough, for supplying fuel to the air flowing therethrough foradmixture therewith; a tubular member disposed generally normal to thedirection of flow of the fuel-air mixture through said chamber andproviding an ignition surface; second wall structure defining a heatingchamber having an inlet wall downstream of the fuel supply means, saidinlet being directed upstream in the main combustion chamber for entryof a limited portion of the fuel-air mixture flowing through said mainchamber, and said heating chamber having an outlet forburning gasescommunicating with the interior of the tubular member, and means 8550?ciated with said heating chamber for initiating combustiontherein, saidtubular member having one or more outlet openings in the downstream sidethereof, whereby burning gases and hot products of combustion dischargedfrom the heating chamber to the interior of the tubular member may flowthrough the latter and heat the ignition surface thereof to theauto-ignition temperature of the main fuel-air mixture flowing incontact with the said surface.

2. Structure as specified in claim 1, wherein the tubular member ha aseries of outlet openings in the downstream side thereof throughout amajor portion of its length.

3. Structure as specified in claim 1, wherein the tubular member has anoutlet slot in the downstream side thereof extending throughout a majorportion of its length.

i. Structure as specified in claim 1, wherein the tubular member has aplurality of inlet openings in its upstream side for entry thereto oflimited quantities of fuel-air mixture for combustion therein.

5. In combustion apparatus, first wall structure defining a maincombustion chamber adapted for flow of fuel-air mixture therethrough, aplurality of tubular members extending generally normal to the directionof flow of the mixture through the chamber and providing a plurality ofignition surfaces, second wall structure defining one or more heatingchambers each having an inlet directed upstream in the main combustionchamber for admission to the heating chamber or chambers of a limitedportion of the fuel-air mixture flowing through the main combustionchamber and having an outlet for burning gases communicating with theinteriors of the tubular members, and means associated with said one ormore heating chambers for initiating combustion therein, each of saidtubular members having one or more outlet openings in the downstreamsides thereof, whereby burning gases and hot products of combustiondischarged from the heating chamber or chambers may flow through thetubular members and heat the ignition surfaces thereof to theauto-ignition temperature of the main fuel-air mixture flowing incontact with the said surfaces.

WALTER D. POUCHOT.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,482,505 Pierce Sept. 20, 1949 2,508,520 Bedding May 23,1950;

